A new species of Hemigrammus from the upper rio Negro basin, Brazil, with comments on the presence and arrangement of anal-fin hooks in Hemigrammus and related genera (Ostariophysi: Characiformes: Characidae)

A new species of Hemigrammus is described from the rio Tiquié, a tributary of the rio Uaupés, upper rio Negro basin, Amazonas, Brazil. The new species can be distinguished from all congeners by the presence (in life specimens) of an orange blotch, situated between the two dark humeral blotches, immediately ahead and slightly above the posterior, darker second humeral blotch. Additionally, the new species can be distinguished from all congeners, except H. haraldi, H. luelingi, H. neptunus, H. ocellifer, H. pretoensis, and H. pulcher, by the possession of two humeral blotches. It can be distinguished from these species by lacking a blotch on the caudal peduncle (vs. caudal peduncle blotch present). A monophyletic group within Hemigrammus, the Hemigrammus ocellifer species-group, encompassing the new species, plus Hemigrammus ocellifer, H. neptunus, H. guyanensis, H. luelingi, H. pulcher, and H. haraldi, is proposed, based on the shared possession of a derived hook arrangement in the anal-fin of mature males and some pigmentary features. A discussion of the hooks’ presence and arrangement within the genus Hemigrammus and in the related genera Parapristella and Petitella is presented, based on an extensive examination of specimens belonging to these genera. It is hypothesized that the close association between anal-fin hooks and dense, presumably secretory tissue, found in all Hemigrammus, Parapristella, Petitella, and Hyphessobrycon species examined, is a mechanism to facilitate cell rupture, enhancing the setting free of cell secretions.

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VARI, R. P. & FERRARIS JR, C. J. 2004. A new species of Nannocharax (Characiformes: Distichodontidae) from Cameroon, with the description of contact organs and breeding tubercles in the genus. Proceedings of the BiologicalSociety of Washington 117 (4): 551-563.

WEITZMAN, S. H. & FINK, W. L. 1983. Relationships of the neon tetras, a group of South American freshwater fishes (Teleostei, Characidae), with comments on the phylogeny of New World characiforms. Bulletin of theMuseum of Comparative Zoology 150 (6): 339-395.

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A new species of Hemigrammus from the upper rio Negro basin, Brazil, with comments on the presence and arrangement of anal-fin hooks in Hemigrammus and related genera (Ostariophysi: Characiformes: Characidae)